can an mbbs doctor practice law and medicine ,if so how can he join llb without writing entrance

No. You can be practitioner of only one of the two professions. There is no objection for studying llB search for " law colleges' in Google

quite a strange question from the doc.......legal profession is no fun.......u can not pursue medicine and legal practice together. without getting into entrance test u fit for academic degree which will not give u any license to practice as a lawyer, though u can procure regular degree from certian mischevious kind of universities. better u remain doc.